Embodiments of the disclosure provide methods of fabricating a thin film transistor device with good profile control of peripheral sidewall of an active layer formed in the thin film transistor devices. In one embodiment, a method for manufacturing a thin film transistor device includes providing a substrate having a source-drain metal electrode layer disposed on an active layer formed thereon, wherein the active layer is a metal oxide layer, performing a back-channel-etching process to form a channel in the source-drain metal electrode layer, and performing an active layer patterning process after the back-channel-etching process.